Question

如何在interItemSpacing中获得水平流布局的实际UICollectionView？我能获得（和设置）的唯一信息是minimumInteritemSpacing。

我需要它，为了以下小计算，总是在集合视图中显示3个相等宽度的项目，而不管屏幕大小（我想用公式中的interItemSpacing的当前值替换minimumInteritemSpacing）： flowLayout.itemSize = CGSizeMake((_collectionView.frame.size.width/3.0)-(flowLayout.minimumInteritemSpacing/3.0), _collectionView.frame.size.height);我将此计算放在viewDidLayoutSubviews中，并且它在某些屏幕上无法正常工作，因为它们的当前interItemSpacing与minimumInteritemSpacing不同

提前感谢。

Answer 1

您可以通过比较两个连续的单元格来获得实际间距

类似

let firstIndex =  IndexPath(item: 0, section: 0)
let secondIndex = IndexPath(item: 1, section: 0)
if let att1 = collectionView.layoutAttributesForItem(at: firstIndex),
let att2 = collectionView.layoutAttributesForItem(at: secondIndex) {
  let actualSpace = att2.frame.minX - att1.frame.maxX
  print (actualSpace)
}

Answer 2

要创建具有固定间距的单元格，请尝试：

private let minItemSpacing: CGFloat = 8
private let itemWidth: CGFloat      = 100
private let headerHeight: CGFloat   = 32

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()

    // Create our custom flow layout that evenly space out the items, and have them in the center
    let layout = UICollectionViewFlowLayout()
    layout.itemSize = CGSize(width: itemWidth, height: itemWidth)
    layout.minimumInteritemSpacing = minItemSpacing
    layout.minimumLineSpacing = minItemSpacing
    layout.headerReferenceSize = CGSize(width: 0, height: headerHeight)

    // Find n, where n is the number of item that can fit into the collection view
    var n: CGFloat = 1
    let containerWidth = collectionView.bounds.width
    while true {
        let nextN = n + 1
        let totalWidth = (nextN*itemWidth) + (nextN-1)*minItemSpacing
        if totalWidth > containerWidth {
            break
        } else {
            n = nextN
        }
    }

    // Calculate the section inset for left and right. 
    // Setting this section inset will manipulate the items such that they will all be aligned horizontally center.
    let inset = max(minItemSpacing, floor( (containerWidth - (n*itemWidth) - (n-1)*minItemSpacing) / 2 ) )
    layout.sectionInset = UIEdgeInsets(top: minItemSpacing, left: inset, bottom:    minItemSpacing, right: inset)

    collectionView.collectionViewLayout = layout
}

有关更多信息，请阅读以下文章：

http://samwize.com/2015/11/30/understanding-uicollection-flow-layout/

获取实际的UICollectionView项间距

2 个答案: